Abstract: A device for aligning a guide template used in resecting a distal femur in a one-compartment joint replacement. The device includes first and second support members (12;5), at least one rod-like transverse coupler (10;12), and a guide template (20). The support members each include a support surface (3;6) that is adjustable to lie in one plane (1) and designed to bear against one condyle (24;25) of a femur (21). The transverse coupler is arranged parallel to a transverse axis (2), which, in its end portion, is connected to the first support member (12) and is releasably connectable to the second support member (5). The transverse axis (2) extends parallel to a plane (1). The guide template (20) is displaceable parallel to the plane (1) relative to the second support member (5) and releasably lockable thereon.